A typical multi-speed transmission uses several torque transmitting devices, such as friction clutches, to achieve a plurality of forward and reverse gear or speed ratios, a Neutral, and a Park. Selection of speed ratios is typically accomplished by engaging a shift lever or other driver interface device that is connected by a shifting cable or other mechanical connection to the transmission. Alternatively, the selection of speed ratios may be controlled by an electronic transmission range selection (ETRS) system, also known as a “shift by wire” system. In an ETRS system, selection of speed ratios is accomplished through electronic signals communicated between the driver interface device and the transmission. The ETRS system reduces mechanical components, increases instrument panel space, enhances styling options, and eliminates the possibility of shifter cable misalignment with the transmission range selection levers.
While previous hydraulic control systems are useful for their intended purpose, the need for new and improved hydraulic control system configurations within transmissions which exhibit improved performance, especially from the standpoints of efficiency, responsiveness and smoothness, is essentially constant. Accordingly, there is a need for an improved, cost-effective hydraulic control system for use in a hydraulically actuated automatic transmission.